What is the importance of the Maple Tree Apartments in the novel, Olive, Again?

The Maple Tree Apartments are an assisted living community in Crosby. Numerous characters move in there at the end of the novel and a microcosmic community of Crosby forms, complete with cliques and gossip. The Maple Tree Apartments have a separate zone for residents who are no longer able to take care of themselves, moving into which is referred to as going "across the bridge."